Set after the events in Trace 1, the narrative of this story follows Han Sihyun, a National Investigation Service (NIS) detective. His mission to establish understanding and coexistence with "Troubles" instead of eliminating them leads him to repeatedly propose a communication research to the NIS, to no avail. After being rejected once more, Sihyun, under the influence of alcohol, illegally captures a "Trouble" and conducts unauthorized experiments on it. Despite initial difficulty in communicating, Sihyun and the "Trouble" develop a lasting bond over time.
